The present invention relates to video record/playback systems and, more particularly, to a system wherein multiple views are simultaneously recorded and are selectable and changeable at playback time.
Continuous loop record and playback devices are well known in the art. For example, as shown in FIG. 1, the so-called "8-Track" cartridge, generally indicated as 10, which is used for audio recording/playback, comprises a housing 12, having an extended loop of magnetic tape 14 therein. As shown by the arrows, in use, the tape 14 is pulled out of the center of a coiled portion 16 across readheads 18 and is wound back onto the outside of the coiled portion 16.
One of the more recent video record/playback devices is the laser video disk such as that shown simplified in FIG. 2. The disk is recorded in a studio and played back with, for example, a home television set and disk player. In the video disk system, generally indicated as 20, at playback time, the video disk 22 is rotated on shaft 24 by motor 26. A laser beam 28 from source 30 passes through the disk 22 to strike a photodetector 32. Information within the disk 22 as recorded therein modulates the laser beam 28 as it passes therethrough such that the electrical signal on lines 34 is a reflection of the information on the disk 22 and can be used to drive a video display.
In both of the aforementioned devices, a sequencing system is provided to move the reading apparatus from track to track. As shown in FIG. 3, the tape 14 of the 8-track cartridge 10 is divided into four major tracks 36 across the width of the tape 14. Each track 36 is subdivided into two subtracks comprising the "A" and "B" channels of the stereo system. Readheads 18 comprise a side-by-side pair of identical heads 38 and 40 assigned to the A and B channels, respectively. As shown in FIG. 3(a), the heads 18 are initially positioned at track number 1. As the tape 14 is moved past the heads 18, head 38 reads the channel A information on track number 1, and head 38 reads the channel B information and electrical signals reflecting that data are developed on lines 42 and 44, respectively, which can be amplified and output as stereo music reflecting the contents of track number 1. Upon track number 1 arriving at a point thereon with an "end of track" marker (not shown), the heads 18 are skipped one track to the position of FIG. 3(b) where they are reading the data from track number 2. Upon reaching the "end of track" on track number 2, the heads 18 are skipped one more track to track number 3 as shown in FIG. 3(c). Similarly, at the "end of track" of track 3, the heads 18 are shifted to track 4 as shown in FIG. 3(d). At the end of track 4, the heads 18 are again skipped one track from track 4 to track 1 which, physically, involves skipping back over tracks 2 and 3 to the track number 1 position. Typically, a user "skip" button is provided which, when pushed, causes the heads 18 to skip to the next track 36 as if the "end of track" signal had been read. In addition to the more commonly known stereo players, such a system was also used in a robot toy game manufactured and sold by MEGO under the name "2XL".
Turning to FIG. 4, the disk 22 of the video disk system 20 of FIG. 2 is shown in plan view with a typical data track layout shown and numbered. In this particular instance, the tracks 46 comprise consecutive rings on the disk 22. Each track 46 begins and ends at the same point. As the disk 22 rotates between the laser source 30 and the photodetector 32, an appropriate sensing mechanism (not shown) senses the end of track, i.e. vertical intervals, (indicated by the dashed line 48) and causes an appropriate mechanism (also not shown for simplicity) to skip the laser source 30 and photodetector 32 in combination inward towards the shaft 24 in the direction of the arrows 50 one track 46. Typically, for convenience, each track 46 represents one "frame" on the video display. Thus, for example, if 30 frames are shown each second as with standard NTSC television to prevent flicker, a typical one and one-half hour television motion picture would occupy approximately 181,000 tracks 46 on each of two sides of disk 22.
Basic prior art switching logic for a video disk system such as that shown as 20 in FIG. 2 and as described with respect to FIG. 4 is shown in FIG. 5. At decision block 5.1 the logic checks for the end of track 48. If it is the end of track, at action block 5.2 the logic skips the laser source 30 and photodetector 32 in combination one track as just described. In either case, the logic next checks at decision block 5.3 as to whether a "skip" has been requested. This feature is typically provided in the manner of the skip button described with respect to FIG. 3 whereby the heads 18 could be jumped from track to track. Quite often, a video disk system will have a "fast forward" button wherein the viewer can repeatedly skip over tracks to find a desired portion of the disk. When video disks are applied to such applications as video games, the logic of FIG. 5 is quite often produced wherein the mechanism can be skipped on request by the program to a particular track on the disk in order to display known action recorded at that point. Thus, if a skip is requested at decision block 5.3, at action block 5.4 the logic picks up the new track number, at action block 5.5, it skips one track towards the new track, and at decision block 5.6, it checks to see if it is at the new track; if it is, it returns to the beginning of the loop to check for end of track and, if not, it returns to action block 5.5 to skip one more track.
Easily implemented additional features are often provided in conjunction with the "skip to next track" block 5.2 in a disk system. These are shown in the additional logic of FIG. 6. Having found the end of track at decision block 5.1, as duplicated in FIG. 6, at decision block 6.1 the logic next checks to see if "stop action" has been selected. If it has, the viewer is simply requesting that the action not proceed. This is easily done by by-passing the "skip to the next track" and allowing the same track to repeat over and over until the stop action has been deleted. If stop action has not been selected, at decision block 6.2 the logic checks to see if "slow motion" has been selected. If it has, a simple delay, as implemented at action block 6.3, before skipping to the next track will cause the motion to be slowed down.
While the foregoing features of the prior art record and playback systems are desirable and provided obvious benefits, they are unable to provide selection of multiple views as would be desirable in certain applications. For example, in a self-study program implemented on a video disk system, a student surgeon (or practicing surgeon looking for self-improvement) might watch a particular surgical technique on a video disk. At various points in the procedure, the student might desire and also receive benefit of a view of the procedure from a different angle than that presently on the screen. In prior art systems, there is no ability for him to see that view unless it is the view originally selected at the time of the video recording of the surgical procedure; or, unless several views are serially recorded, say a minute or two per view, and then viewed successively. The latter approach may present all the desirable views, but cannot do so in real time and, therefore, destroys the continuity required for learning a complex surgical procedure or the like. Wherefore, it is the object of the present invention to provide a video recording and playback system wherein multiple simultaneous views are recorded which can be individually selectable and changeable at the time of viewing.